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        <h2>
          <span class="refentrytitle">moogvcf</span>
        </h2>
        <p>moogvcf — 
      A digital emulation of the Moog diode ladder filter configuration.
    </p>
      </div>
      <div class="refsect1">
        <a id="idp126365392"></a>
        <h2>Description</h2>
        <p>
      A digital emulation of the Moog diode ladder filter configuration.
    </p>
      </div>
      <div class="refsect1">
        <a id="idp126366672"></a>
        <h2>Syntax</h2>
        <pre class="synopsis">ares <span class="command"><strong>moogvcf</strong></span> asig, xfco, xres [,iscale, iskip]</pre>
      </div>
      <div class="refsect1">
        <a id="idp126368848"></a>
        <h2>Initialization</h2>
        <p>
      <span class="emphasis"><em>iscale</em></span> (optional, default=1) -- internal
    scaling factor. Use if <span class="emphasis"><em>asig</em></span> is not in the
    range +/-1. Input is first divided by <span class="emphasis"><em>iscale</em></span>,
    then output is mutliplied <span class="emphasis"><em>iscale</em></span>. Default
    value is 1. (New in Csound version 3.50)
    </p>
        <p>
      <span class="emphasis"><em>iskip</em></span> (optional, default=0) -- if non zero
    skip the initialisation of the filter. (New in Csound version
    4.23f13 and 5.0)
    </p>
      </div>
      <div class="refsect1">
        <a id="idp126436064"></a>
        <h2>Performance</h2>
        <p>
      <span class="emphasis"><em>asig</em></span> -- input signal
    </p>
        <p>
      <span class="emphasis"><em>xfco</em></span> -- filter cut-off frequency in Hz. As of version 3.50, may i-,k-, or a-rate.
    </p>
        <p>
      <span class="emphasis"><em>xres</em></span> -- amount of resonance. Self-oscillation occurs when <span class="emphasis"><em>xres</em></span> is approximately one. As of version 3.50, may a-rate, i-rate, or k-rate.
    </p>
        <p>
      <span class="emphasis"><em>moogvcf</em></span> is a digital emulation of the Moog diode ladder filter configuration. This emulation is based loosely on the paper <span class="quote">“<span class="quote">Analyzing the Moog VCF with Considerations for Digital Implementation</span>”</span> by Stilson and Smith (CCRMA). This version was originally coded in Csound by Josep Comajuncosas. Some modifications and conversion to C were done by Hans Mikelson.
    </p>
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              <th align="left">Warning</th>
            </tr>
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              <td align="left" valign="top">
                <p>Before version 6.02 this filter required that the input signal be normalized to one. This can be easily achieved using <a class="link" href="Zerodbfs.html" title="0dbfs"><em class="citetitle">0dbfs</em></a>, like this:
      </p>
                <div class="literallayout">
                  <p>ares <span class="command"><strong>moogvcf</strong></span> asig, kfco, kres, 0dbfs</p>
                </div>
                <p>You can also use <a class="link" href="moogvcf2.html" title="moogvcf2"><em class="citetitle">moogvcf2</em></a> which defaults scaling to <a class="link" href="Zerodbfs.html" title="0dbfs"><em class="citetitle">0dbfs</em></a>. </p>
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      <div class="refsect1">
        <a id="idp126447472"></a>
        <h2>Examples</h2>
        <p>
      Here is an example of the moogvcf opcode. It uses the file <a class="ulink" href="examples/moogvcf.csd" target="_top"><em class="citetitle">moogvcf.csd</em></a>.
      </p>
        <div class="example">
          <a id="idp126449328"></a>
          <p class="title">
            <strong>Example 526. Example of the moogvcf opcode.</strong>
          </p>
          <div class="example-contents">
            <p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
            <pre class="programlisting">
<span class="csdtag">&lt;CsoundSynthesizer&gt;</span>
<span class="csdtag">&lt;CsOptions&gt;</span>
<span class="comment">; Select audio/midi flags here according to platform</span>
-odac   <span class="comment">;;;realtime audio out</span>
<span class="comment">;-iadc    ;;;uncomment -iadc if realtime audio input is needed too</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o moogvcf.wav -W ;;; for file output any platform</span>
<span class="csdtag">&lt;/CsOptions&gt;</span>
<span class="csdtag">&lt;CsInstruments&gt;</span>

<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">ksmps</span> <span class="op">=</span> 32
<span class="ohdr">nchnls</span> <span class="op">=</span> 2
<span class="ohdr">0dbfs</span>  <span class="op">=</span> 1

<span class="oblock">instr</span> 1
<span class="comment">; iscale does not need to be set here because already 0dbfs = 1  </span>
aout <span class="opc">vco</span> .3, 220, 1	<span class="comment">; Use a nice sawtooth waveform.</span>
kfco <span class="opc">line</span> 200, p3, 2000	<span class="comment">; filter-cutoff frequency from .2 to 2 KHz</span>
krez <span class="opc">init</span> p4
asig <span class="opc">moogvcf</span> aout, kfco, krez
     <span class="opc">outs</span> asig, asig

<span class="oblock">endin</span>
<span class="csdtag">&lt;/CsInstruments&gt;</span>
<span class="csdtag">&lt;CsScore&gt;</span>
<span class="comment">;a sine wave</span>
<span class="stamnt">f</span> 1 0 16384 10 1

<span class="stamnt">i</span> 1 0 3 .1
<span class="stamnt">i</span> 1 + 3 .7
<span class="stamnt">i</span> 1 + 3 .95
<span class="stamnt">e</span>
<span class="csdtag">&lt;/CsScore&gt;</span>
<span class="csdtag">&lt;/CsoundSynthesizer&gt;</span>
</pre>
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        <p><br class="example-break" />
    </p>
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      <div class="refsect1">
        <a id="idp126453616"></a>
        <h2>See Also</h2>
        <p>
      <a class="link" href="moogvcf2.html" title="moogvcf2"><em class="citetitle">moogvcf2</em></a>,
      <a class="link" href="biquad.html" title="biquad"><em class="citetitle">biquad</em></a>,
      <a class="link" href="rezzy.html" title="rezzy"><em class="citetitle">rezzy</em></a>
    </p>
      </div>
      <div class="refsect1">
        <a id="idp126457584"></a>
        <h2>Credits</h2>
        <p>
      </p>
        <table border="0" summary="Simple list" class="simplelist">
          <tr>
            <td>Author: Hans Mikelson</td>
          </tr>
          <tr>
            <td>October 1998</td>
          </tr>
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        <p>
    </p>
        <p>New in Csound version 3.49</p>
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